使用后台线程从 url 加载注释.在移动或缩放 mapView 之前 Pins 不显示 [英] Loading annotations from url using background thread. Pins doesn't show before moving or scaling mapView

问题描述

我使用后台线程从 url 加载注释.在我移动或缩放 mapView 之前，引脚不会显示.如何更新我的视图?

I load annotations from url using background thread. Pins doesn't show before I move or scale mapView. How can I update my view?

我的 viewDidAppear

My viewDidAppear

- (void)viewDidAppear:(BOOL)animated
{

[super viewDidAppear:animated];

//Create the thread 
[NSThread detachNewThreadSelector:@selector(loadPList) toTarget:self withObject:nil];

}

loadPList

- (void) loadPList { //Load the plist NSString *urlStr = [[NSString alloc] initWithFormat:@"http://www.domain.com/data.xml"];

NSURL *url = [NSURL URLWithString:urlStr]; NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfURL:url];

NSMutableArray *annotations = [[NSMutableArray alloc]init];

NSArray *annotationsOnMap = mapView.annotations; if ([annotationsOnMap count] > [annotations count]) { [mapView removeAnnotations:annotationsOnMap];

} else { //Do nothing }

if ([[NSUserDefaults standardUserDefaults] boolForKey:@"blackKey"]) {

NSArray *ann = [dict objectForKey:@"Category1"];

for(int i = 0; i < [ann count]; i++) {

    NSString *coordinates = [[ann objectAtIndex:i] objectForKey:@"Coordinates"];

    double realLatitude = [[[coordinates componentsSeparatedByString:@","] objectAtIndex:1] doubleValue];
    double realLongitude = [[[coordinates componentsSeparatedByString:@","] objectAtIndex:0] doubleValue];

    MyAnnotation *myAnnotation = [[MyAnnotation alloc] init];
    CLLocationCoordinate2D theCoordinate;
    theCoordinate.latitude = realLatitude;
    theCoordinate.longitude = realLongitude;

    myAnnotation.coordinate=CLLocationCoordinate2DMake(realLatitude,realLongitude);

    myAnnotation.title = [[ann objectAtIndex:i] objectForKey:@"Name"];
    myAnnotation.subtitle = [[ann objectAtIndex:i] objectForKey:@"Address"];
    myAnnotation.icon = [[ann objectAtIndex:0] objectForKey:@"Icon"];


    [mapView addAnnotation:myAnnotation];
    [annotations addObject:myAnnotation];



}
}

else { //Do nothing }

//And same with other categories....

//Update the ui dispatch_async(dispatch_get_main_queue(), ^{

}); }

推荐答案

您正在从非 UI 更新 UI - 线程这将不起作用

You are updating the UI from a non UI - Thread this will not work

您必须调用代码段来更新 UIThread 块内的 ui，如下所示:

You will have to call segments of code that update your ui inside the UIThread Block as following:

例如

[mapView removeAnnotations:annotationsOnMap];

必须在 UI-Thread 中调用

must be called in UI-Thread

   dispatch_async(dispatch_get_main_queue(), ^{
        //Update UI if you have to
        [mapView removeAnnotations:annotationsOnMap];
    });

请注意，您必须在 main_queue 线程中调用所有 UI 更新

Please note that you have to call all your UI updates inside the main_queue thread

   dispatch_async(dispatch_get_main_queue(), ^{
        //All UI updating code must come here
    });

这篇关于使用后台线程从 url 加载注释.在移动或缩放 mapView 之前 Pins 不显示的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！